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Force transmissibility of a nonlinear vibration isolator with high-static-low-dynamic-stiffness

Alessandro Carrella

A problem that affects many engineering application is that of reducing the level
of vibration transmitted from a source to a receiver. A lower natural frequency
would benefit the isolation performance of a vibration isolator because it would
provide a wider frequency isolation region. However, if a linear mount is used,
this approach is limited by the static displacement that derives from a soft
spring. One possible solution is to employ nonlinear mounts with
high-static-low-dynamic-stiffness (HSLDS) whose dynamic can be often described by
the Duffing equation. Although the response of the Duffing oscillator to a harmonic
force applied to the mass has been extensively studied, an analytical formulation
of the transmissibility of these systems is not available. In this paper a simple
expressions for the maximum transmissibility is proposed. Furthermore, the
transmissibility of an HSLDS isolator is compared with that of an equivalent linear
model to show the improved performance.